GB480577A - Improvements in or relating to ultra high frequency radio systems - Google Patents

Abstract

480,577. Wireless systems. MARCONI'S WIRELESS TELEGRAPH CO., Ltd. July 19, 1937,No. 19900. Convention date, July 18, 1936. [Class 40 (v)] [Also in Group XXXV] In a short-wave wireless system, constancy of communication beyond the optical range is preserved, despite changes in atmospheric ionization and the like, by employing two aerials at the receiver and utilizing any difference in their received signal strength to vary the transmitter frequency, or the vertical angle of propagation, so as to restore equality. The two receiving-aerials 29, 31 are connected to frequency-changing circuits 33, 35 fed by a common local oscillator 37. The detectors 43, 45 apply to the grids of the valves 47, 49 voltages proportional to the received signals. The plate circuits of these valves include an alternating source 55, which may be the mains supply, the opposed field coils 51, 53 of a motor 57, and output transformers 52, 54 feeding the lines 63, 65. When unequal reception occurs, the motor 57 operates through gearing 61 to adjust the tuning of the local oscillator. Unequal currents are also sent back to the transmitter along the lines 63, 65 to amplifiers and rectifiers which apply unequal voltages to the grids of valves 75, 77 with the result that a motor 85 starts in one direction or the other and through gearing 89 adjusts the transmitter frequency until equality of reception is again obtained in the receiving- aerials 29, 31. If the receiver is broadly tuned, its adjustment may be unnecessary. The lines 63, 65 may be replaced by a long-wave radio link. In a modification, the motor 85, instead of varying the frequency, adjusts the vertical angle of propagation of the waves, e.g. by tilting the aerial. In this case the motor 57 is omitted.